Amine hydrochlorides in refinery overheads: Solving corrosion problems through electrolyte process simulation Prodip Kundu OLI Systems Inc. 2014 Software Global Customer Conference September 30 - October 2, 2014 Refinery overhead corrosion  Contain complex mixtures of hydrocarbons, water, inorganic and organic acids, and various ionic species.  Composition and phase behavior changes rapidly as it is being condensed.  Acids or salts present in the overhead system can cause corrosion when the right conditions exist.  Organic neutralizing amines are commonly used to combat corrosion in refinery crude column overhead systems.  Corrosion due to neutralizing amines in refinery overhead systems and subsequent corrosion-related failures are frequently reported.  In order to avoid expensive material solutions (i.e., Ti), we need to understand the overhead chemistry better. Refinery overhead corrosion Acidic chloride-based corrosion: Residual salts hydrolysis: Amine hydrochloride salts formation: RNH v + HCl v ↔ RNH Cl s/l 2 3 + − RNH Cl s/l + H O ↔ RNH aq + Cl (aq) 3 2 3 Refinery overhead corrosion Root Cause of Failures:  Failures can be traced to the formation of amine hydrochlorides, either as hygroscopic solids or concentrated solutions.  Lack of understanding of physical properties, thermochemical behavior and phase equilibria of amines and their hydrochloride salts. OLI Systems’ Mixed-Solvent Electrolyte (MSE) model:  Phase equilibria in mixtures containing various amines, ammonia, HCl, CO , 2 H S, water and hydrocarbons. 2  The model predicts the formation of solid salts or concentrated amine hydrochloride solutions that may induce corrosion. Mixed-solvent electrolyte model (MSE): Thermophysical Framework Gas-phase Excess Gibbs Thermo- equation of energy model chemistry of state species Standard-state Adsorption properties of Themodynamic models solution framework species Phase and Transport chemical properties and equilibrium surface tension algorithm Applications (process, corrosion, oilfield scaling, etc.) Structure of the thermodynamic model  Definition of species that may exist in the liquid, vapor, and solid phases  Excess Gibbs energy model for solution nonideality  Calculation of standard-state properties Helgeson-Kirkham-Flowers equation for ionic and neutral  aqueous species Standard thermochemistry for solid and gas species   Algorithm for solving phase and chemical equilibria Standard-state properties: Aqueous species  Helgeson-Kirkham-Flowers-Tanger equation  Temperature and pressure dependence of partial molar volumes and heat capacities based on ion solvation theory  Computation of standard-state Gibbs energy and enthalpy of formation and entropy by thermodynamic integration  Estimation methods for the HKF parameters Outline of the model: Solution nonideality ex ex ex ex G G G G Excess Gibbs energy  LR  LC  II RT RT RT RT LR Debye-Hückel theory for long-range electrostatic interactions LC Local composition model (UNIQUAC) for neutral molecule interactions II Ionic interaction term for specific ion-ion and ion- molecule interactions Gex   II  n  x x B I  ion interaction parameters  i  i j ij x RT   i i j B ( I )  b  c exp(  I  a ) ij x ij ij x 1 Outline of the model: Chemical equilibrium calculations For a sample chemical reaction: aA  bB  cC  dD Standard-state chemical potential of i At equilibrium G0  xc  xd c d    ln C D  C D  0 0   with G  v  RT  xa  xb a b  i i A B A B i  Solu bility and vapor-liquid equilibria are governed by analogous equations  Infinite-dilution properties Thermochemical databases for aqueous systems  Helgeson-Kirkham-Flowers model for T and P dependence  MSE-AmineHCL Databank Thermodynamic Framework Mixed-solvent electrolyte model (MSE) Subset of the chemistry of interest (i.e., CO , H S, H O, 2 2 2 Parameters for NH , HCL, NH CL, 56 Hydro- 3 4 amine hydrochlorides carbons and selected mixtures) MSE Databank AmineHCL Databank Private databank, available MSE Databank only to consortium members until November 15, 2014 New MSE databank, available from November 15, 2014